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Catch the rainwater harvesting wave to cut your business’s wastewater costs, irrigation requirements, and even indoor water consumption. Rainwater catchment systems can be used to collect water for toilet flushing, manufacturing processes, cooling towers, fire suppression, cleaning, laundry, and even drinking and cooking. Green roofs can also be integrated into a rainwater collection system to augment water filtration.

How to harvest rainwater

For most businesses, installing a rainwater collection system is no small matter, most often requiring the services of experts in the field. To find someone in your area, consult this American Rainwater Catchment Systems Association Business Directory.

But first, get your mental juices flowing with these general rainwater harvesting guidelines:

1. Collector size: The size of your building (the roof, in particular) will be the biggest factor in determining what size your rainwater catchment system needs to be. In general, the maximum storage capacity required can be calculated by multiplying the square footage of your roof by three. Then, depending on the collector size needed, you can choose from one of two basic catchment options:
   • Larger buildings will no doubt require large stormwater collection systems consisting of proportionately sized cisterns (which can be above or below ground), pressuring equipment (pressure vessels, pumps, etc.), water- purifying equipment, and so on. This rainwater collection method often requires a graywater system through which rainwater is recycled and reused for internal water fixtures, such as toilets and irrigation systems.
   • Smaller buildings and home-based businesses are more likely to employ simple rain barrel systems that connect to conventional downspouts, collecting much smaller volumes of water. These systems are seldom hooked into a building’s water system.
2. Regulatory considerations: State and federal governments sometimes implement rainwater collection guidelines and reuse standards, occasionally requiring that water be filtered before it is reused for other purposes. Check with your community water regulator before beginning your project to avoid any headaches. These Guidelines for Water Reuse from the US Environmental Protection Agency (EPA) may also be a helpful resource.
3. LEED your way to a greener building: Don’t forget that rainwater harvesting systems qualify for LEED credits.

Installing a rainwater harvesting system helps you go green because…

• They allow you to recycle water, thereby cutting down on use of fresh, potable water.
• They reduce the amount of water entering your local community's sewage system, and act as a buffer against contaminated runoff during heavy storms.

Buildings, including commercial, residential, and educational, consume approximately 20 percent of the total water drawn from fresh sources every day. Reducing this amount by a mere 10 percent would save over 2 trillion gallons of fresh water annually.[1] Rain harvesting can go a long way toward reducing a business’s dependence on the local water system, which ultimately means lower water and wastewater bills. The Lady Bird Johnson Wildflower Center in Austin, Texas, has installed extensive rainwater collection systems throughout the campus, collecting water from 17,000 square feet of roof space and storing it in tanks that can accommodate 70,000 gallons of water. This system supplies 10 to 15 percent of the center's garden and landscaping irrigation.[2]

Another significant benefit to installing rainwater collection systems on commercial buildings is the reduction in stormwater runoff. During periods of heavy rain, many communities' stormwater systems become overloaded, causing sewers to spill over into local lakes, streams, and rivers. This runoff is often contaminated and can cause serious community health problems. Rain barrels capture rainwater during heavy storms and thus help prevent local sewers from being contaminated.[3] Approximately 620 gallons of water can be collected for every inch of rain falling on a 1,000 square foot roof—water which would have otherwise run into the stormwater system.[4] Seattle City Hall has incorporated a rainwater collection system that has allowed the occupants to reduce stormwater runoff by 75 percent, in addition to cutting potable water demand.[5]

Additional benefits of rainwater collection systems include decreased energy demand for water filtration and pumping systems and reduction in water taken from rivers and groundwater supplies.[6]

External links

• International Rainwater Catchment Systems Association
• Western Regional Climate Center - Historical Precipitation Maps by State
• University of Arizona Cooperative - Harvesting Rainwater for Landscape Use
• Water, Use it Wisely - Your Local Water Authority’s Water Conservation Programs
• Business for Social Responsibility - At the Crest of a Wave: A Proactive Approach to Corporate Water Strategy
• Duke University Libraries - A Cost-Benefit Analysis of Rainwater Harvesting at Commercial Facilities in Arlington County, Virginia
• Using Rainwater to Grow Livable Communities - Toolbox Find resources for planning and communicating your rainwater collection goals and successes.